While the gain makes the Bakken the fastest-growing oil field in the world, the new numbers are still lower than Oklahoma City-based Continental Resources' estimates.

The government now says the Bakken likely holds about 7.4 billion barrels of undiscovered oil that can be recovered with today's technology. The number does not include the amount of oil companies have proved is in the ground.

“These world-class formations contain even more energy resource potential than previously understood, which is important information as we continue to reduce our nation's dependence on foreign sources of oil,” Interior Secretary Sally Jewell said in a statement Tuesday. “We must develop our domestic energy resources armed with the best available science, and this unbiased, objective information will help private, nonprofit and government decision-makers at all levels make informed decisions about the responsible development of these resources.”

The new oil number is 49 times more than the geological survey's 1995 forecast of 151 million barrels of recoverable oil. By 2008, the geological survey revised its estimate to 3.7 billion barrels.

The geological survey attributed much of its most recent increase to efforts by Continental Resources and other producers to recover oil from the Three Forks Formation, which lies beneath the Bakken in the Williston Basin of North Dakota and Montana.

“Since the 2008 USGS assessment, more than 4,000 wells have been drilled in the Williston Basin, providing updated subsurface geologic data,” the government said in a statement. “Previously, very little data existed on the Three Forks Formation and it was generally thought to be unproductive. However, new drilling resulted in a new understanding of the reservoir and its resource potential.”

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Adam Wilmoth returned to The Oklahoman as energy editor in 2012 after working for four years in public relations. He previously spent seven years as a business reporter at The Oklahoman, including five years covering the state's energy sector....